Among various allergic diseases, especially, asthma is a complex inflammatory disease of the lung characterized by variable airflow obstruction, airway hyperresponsiveness, and airway inflammation. The inflammatory response in the asthmatic lung is characterized by infiltration of the airway wall by mast cells, lymphocytes and eosinophils and is associated with the increased expression of several inflammatory proteins, including cytokines, enzymes, and adhesion molecules in the airways. The T helper 2 (Th2)-type cytokines such as interleukins (IL)-4, IL-5, and IL-13, which are produced by activated CD4+ T cells play a central role in the pathogenesis of asthma by controlling the key process of immunoglobulin E (IgE) production, the growth of mast cells and the differentiation and activation of mast cells and eosinophils. The direction of Th cell differentiation is determined by the cytokine environment at the site of initial antigenic activation. It has been well documented that the presence of IL-4 during the induction phase accounts for a predominance of Th2 cells, which subsequently determine the allergic inflammatory responses. Th2 cells are the predominant lymphocyte population that infiltrates the airways of asthmatics, and the cytokine products of Th2 cells perform essential roles in airway eosinophilia, airway hyperresponsiveness, and serum IgE in animal models.
Meanwhile, marine algae have been consumed in Asia since ancient times, which are rich in vitamins, minerals, dietary fibers, proteins, polysaccharides, etc. Moreover, seaweeds are considered to be a rich source of antioxidant. Hence, many types of seaweed have been examined to identify new and effective antioxidant compounds, as well as to elucidate the mechanisms of cell proliferation, anti-inflammation and apoptosis (Yuan, Y. V. et al., 2006, Antioxidant and antiproliferative activities of extracts from a variety of edible seaweeds, Food and Chemical Toxicology 44, 1144-1150; Heo, S. J. et al., 2006, Antioxidant activities of red algae from Jeju island, Algae 21, 149-156; Nahas, R. et al., 2007, Radical-scavenging activity of Aegean Sea marine algae, Food Chem. 102, 577-581; Kim, S. K. et al., 2008, Effects of Ecklonia cava ethanolic extracts on airway hyperresponsiveness and inflammation in a murine asthma model: Role of suppressor of cytokine signaling, Biomed. Pharmacother. 62, 289-296).
The red algal genus Laurencia has been known to contain natural bioactive materials of polysaccharides, polyphenols, terpenes and the other halogenated secondary metabolites. It has been reported that the red algal genus Laurencia possesses antioxidant, anticancer and antibacterial activities (Liang, H. et al., 2007, Effect of ethanol extract of alga Laurencia supplementation on DNA oxidation and alkylation damage in mice, Asia Pac J. Clin. Nutr. 16, 164-168; Pec, M. K. et al., 1999, Growth inhibition by dehydrothyrsiferol—a non-Pgp modulator, derived from a marine red alga—in human breast cancer cell lines, Int. J. Oncol. 14, 739-743; Vairappan, C. S. et al., 2001, Antibacterial halogenated metabolites from the Malaysian Laurencia species, Phytochemistry 58, 291-297). However, the anti-allergic activity of L. undulata, especially anti-asthmatic activity thereof has never been reported.
As a result of their intensive investigation, the present inventors have discovered that an extract of Laurencia undulata containing a large amount of polyphenols has potent anti-allergic and anti-asthmatic effects.